1. Field of the Invention
The present invention relates to a trochoid oil pump which enables the endurance to be increased and the reduction of discharge pulsations and noise to be achieved and in which those results can be realized with a very simple structure.
2. Description of the Related Art
Japanese Patent Application Laid-open No. H5-215079 discloses that the space between adjacent contraction chambers and the space between the contraction chamber and a discharge chamber are throttled and a gap capable of linking the chambers is formed between the opposing tooth surfaces in which part of the tooth surface on the rear side in the rotation direction of each tooth of the external-tooth gear or part of the tooth surface on the forward side in the rotation direction of each tooth of the internal-contact gear of an internal-contact gear pump is receded over the entire tooth width.
The technological contents disclosed in Japanese Patent Application Laid-open No. H5-215079 is that the recess is formed by flat surfaces over the entire tooth width in part of the tooth surface of the external-tooth gear or internal-tooth gear. Thus, a flat (linear contour) tooth surface is formed on the inner side of the tooth surface (curved contour) with a curved profile in part of the tooth surface with a curved profile, and a recess is formed over the entire tooth width in the tooth surface (curved tooth profile) of the external-tooth gear or internal-tooth gear by the flat tooth surfaces.
When the gap formed by the flat tooth surfaces reaches the discharge chamber after the appropriate contraction of the contraction chamber on the discharge side, a throttled state is assumed. This is because if the drive contact portions in the tooth surfaces of the external-tooth gear or internal-tooth gear are avoided, the size of the flat portions is very limited and the gap constituted by the flat portions also can be only within a limited range. Part of the liquid present in the contraction chamber is discharged via this gap into the adjacent contraction chamber and discharge chamber, following the reduction in volume of the contraction chamber. However, the size of the gap is not held, while enlarging in the rotation direction, correspondingly to the degree of volume reduction of the contraction chamber, the gap soon becomes throttled and a sufficient link to the adjacent contraction chamber is difficult to provide.
For this reason, the amount of the liquid escaping to the adjacent contraction chamber due to contraction is decreased, the excess pressure increase inside the contraction chamber is difficult to prevent, and the noise induced by cavitation is difficult to suppress. It is an object of the present invention to provide an oil pump in which a sufficient link is ensured between an interdental space in a contraction stroke and an adjacent interdental space preceding the interdental space and a sufficient amount of liquid escapes in the interdental space of the contraction stroke, thereby preventing an excess increase in pressure of the fluid inside the interdental space of the contraction stroke and preventing the occurrence of noise and erosion caused by cavitation.
According to the results of a comprehensive study conducted by the inventors with the object of resolving the above-described problems, the first invention resolves the above-described problems by providing a trochoid oil pump in which an interdental space constituted by an inner rotor and an outer rotor having trochoid tooth profile or substantially trochoid tooth profile starts a compression stroke in a partition section between an intake port and a discharge port, a linking gap is composed by the interdental space and a preceding adjacent interdental space realized in a discharge stroke, and the linking gap expands gradually from the start of the compression stroke to the discharge stroke.
Furthermore, the second invention resolves the above-described problems by providing a trochoid oil pump comprising: a rotor chamber 1 comprising an intake port, a discharge port, and a partition section located between the intake port and discharge port; and an inner rotor and an outer rotor having trochoid tooth profile or substantially trochoid tooth profile, wherein, with an interdental space constituted by the inner rotor and outer rotor starting compression after completion of confinement in the partition section between the trailing end portion of the intake port and the leading end portion of the discharge port, a linking gap that links the interdental space and an interdental space that precedes the interdental space and is adjacent thereto is formed by a region without a contact with the tooth profile 5a of the inner rotor formed between the tooth apex portion and the tooth base portion of the tooth profiles of the outer rotor, and the linking gap gradually expands with the rotation of the rotor.
Furthermore, the third invention resolves the above-described problems by providing a trochoid oil pump comprising: a rotor chamber 1 comprising an intake port, a discharge port, and a partition section located between the intake port and discharge port; and an inner rotor and an outer rotor having trochoid tooth profile or substantially trochoid tooth profile, wherein a concave recess portion is formed between the tooth apex portion and the tooth base portion of the tooth profiles of the outer rotor, the interdental space constituted by the inner rotor and outer rotor forms an intake stroke in the intake port, an intake end stroke and a compression stroke in the partition section, and a discharge stroke in the discharge port, a linking gap produced by the recess portion is formed between the interdental space of the compression stroke and an interdental space in the discharge stroke which is preceding and adjacent with respect to the interdental space, and the linking gap gradually expands with the rotation of the rotor.
Furthermore, the fourth invention resolves the above-described problems by providing a trochoid oil pump of the above-described configuration, wherein the shape of the outer peripheral edge in the contactless region of tooth profile 6a of the outer rotor is concaved along a curve in the intermediate portion thereof along a curved line or a circular arc inwardly of the tooth profile. The fifth invention resolves the above-described problems by providing a trochoid oil pump of the above-described configuration, wherein the linking gap maintains continuous expansion from the confinement completion state of the interdental space at least to the compression stroke end state or a state of intersection in the discharge port.
In accordance with the first invention, in the rotation region where the interdental space corresponding to a maximum sealed space is filled with oil (region where cavitation does not occur), the appropriate pressure is released via the linking gap so as to prevent the excess increase in the internal pressure in the interdental space, friction in the rotation drive direction in the tip clearance of the rotor can be reduced and the rotation drive torque can be decreased. Furthermore, in the rotation region where the interdental space that became the maximum sealed space is difficult to fill with oil, the fluid under pressure located in the interdental space adjacent to this interdental space and preceding it in the rotation direction appropriately flows in, thereby making it possible to reduce the difference with the discharge pressure, weaken impacts caused by the difference in pressure, prevent the occurrence of cavitation, and increase the endurance of the product. In addition, drive power loss of the product can be reduced, pulsations can be decreased, and noise can be reduced. The effect of the second invention is almost identical to that of the first invention.
In accordance with the third invention, a concave recessed portion is formed between the tooth apex portion and tooth base portion of the tooth profiles of the outer rotor. As a result, a space of an appropriate size sufficient to constitute the linking gap can be easily formed. Furthermore, because any shape can be produced, various characteristics can be easily set. In accordance with the fourth invention, the recessed portion is concaved along a curve in the intermediate portion thereof along a curved line or a circular arc inwardly of the tooth profile. Therefore, fluid can flow smoothly in the linking gap. In accordance with the fifth invention, the continuous expansion of the linking gap is maintained from the confinement completion state of the interdental space at least to the compression stroke end state or a state of intersection in the discharge port 3. As a result, cavitation can be inhibited, occurrence of erosion can be prevented, and pulsations and noise can be effectively reduced.